1. Field of the Invention
The present invention relates to light-emitting elements using an organic compound, and more particularly, relates to a compound having a molecular structure represented by general formula (1) shown below and an organic electroluminescent (EL) element having stable high efficiency by using the above compound for a light-emitting layer or a charge transport layer.
2. Description of the Related Art
In the past, light emission was typically performed by applying a voltage to an anthracene-deposited film (Thin Solid Films, 94 (1982) 171).
In addition, as particularly described in Macromol. Symp. 125, 1 to 48 (1997), typically, an organic EL element has a structure in which top and bottom electrodes are formed on a transparent substrate and organic material layers, including a light-emitting layer, are provided between the electrodes.
In addition, when various types of fluorescent organic compounds are used, light emission from ultraviolet to infrared can be performed, and, in recent years, research on various compounds have been intensively pursued.
Furthermore, besides organic light-emitting elements using a relatively low molecular weight material as described above, an organic light-emitting element using a conjugated polymer was reported by one group at Cambridge University in Nature, 347, 539 (1990). According to this report, it was confirmed that light emission was obtained from a monolayer film of polyphenylene vinylene (PPV) formed by a coating system.
Based on the recent advances in organic light-emitting elements in which thin and lightweight light-emitting devices have been produced which are characterized by a high luminance at a low applied voltage, a wide spectrum of light-emitting wavelengths, and a high-speed response, it was expected that a wide range of applications of the organic light-emitting element would be realized.
However, it has proven necessary to further improve luminance and/or conversion efficiency. In addition, there have been many problems in durability, such as changes in performance after long term use and degradation thereof caused, for example, by an oxygen-containing gas and/or moisture. Furthermore, when a light-emitting element is applied to a full-color display and the like, light emission of blue, green, and red having superior color purity is required. However, for this application, present device performances have not been satisfactory.
In addition, as a fluorescent organic compound used for an electron transport layer and a light-emitting layer, a large number of aromatic compounds and condensed polycyclic aromatic compounds have been investigated. However, a material having entirely satisfactory light-emission luminance and durability has not been obtained.
Documents bearing on application of fluoranthene compounds to organic EL elements include, Japanese Patent Laid-Open No. 10-189248, and, WO2005026088. Such documents disclose an organic compound having a fluoranthene ring and two biphenyl groups bonded thereto. However, an organic compound of the present invention, which is formed of a fluoranthene ring and a linearly linked oligophenylene group, has believed to be unknown.
When an organic EL element is applied to a display apparatus and the like, apart from high efficiency and highly luminant light emission, sufficient durability must be ensured. However, the above requirements have not been presently sufficiently satisfied.